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Highlights • High-power passively Q-switched Tm:CYA lasers at short wavelengths have been operated. • The operating wavelength was tuned from 1848 to 1876 nm, for the first time. • The tunable Tm:CYA laser is very potential in neural stimulation applications. Abstract Laser emission between about 1850 and 1880 nm is of great interest for neural stimulation applications. We report here on the diode-pumped, continuous-wave and passively Q-switched laser operation of Tm:CaYAlO 4 in this specific wavelength domain, for the first time to our knowledge. In the continuous-wave regime, the maximum output power reaches 5.35 W at 1864 nm with a laser slope efficiency of about 40.5%. Using a Cr:ZnSe saturable absorber, passive Q-switching is achieved with a maximum average output power of 2.37 W at 1857 nm. The narrowest laser pulse width is found to be about 59 ns for a repetition rate of 35.3 kHz and the corresponding laser pulse peak power and pulse energy are about 1.145 kW and 67.5 μJ, respectively. By introducing an undoped YAG crystal as intracavity etalon, tunable and passively Q-switched laser operation is obtained between 1848 and 1876 nm while keeping high pulse energies and peak powers. [ABSTRACT FROM AUTHOR]

• We report the highest output power (12.36 W) of diode-pumped Tm:CALYO laser at 1938 nm with a slope efficiency of 53.9%. • We report the broadest tunability (271 nm) for Tm:CALYO lasers. • Passively Q-switched operation was also achieved with a maximum average output power of 3.81 W and pulse width of 25.9 ns. We report on the recent progress on high-power and broadband wavelength tunability of diode-pumped Tm:CaYAlO 4 (Tm:CALYO) lasers. Using a double-end pumping geometry, we have achieved a maximum output power of 12.36 W at 1938 nm, which is believed to be the highest power that have ever achieved for Tm:CALYO lasers. Moreover, we have operated 1861 nm, 1982 nm and 2032 nm lasers with maximum output powers of 8.73 W, 5.36 W and 0.73 W, respectively, by using differently coated end-face cavity mirrors. Furthermore, using a MgF 2 birefringent filter, we have tuned the lasing wavelengths from 1807 nm to 2078 nm. The 271 nm wavelength range is also believed to be the broadest tunability for Tm:CALYO lasers. Passively Q-switched Tm:CALYO laser has also been demonstrated with a maximum average output power of 3.81 W. The shortest pulse width reached 25.9 ns at a repetition rate of 10.1 kHz, which led to a pulse energy of 377.22 μJ and a peak power of 14.56 kW. These results indicate clearly that the Tm:CALYO crystal is excellent as a high-power and broadband laser gain medium operating at the important 2 μm wavelength region. [ABSTRACT FROM AUTHOR]